Initial Inspection and Diagnostic Overview
INSPECTION AND VERIFICATION1. Verify the customer concern by operating the climate control system to duplicate the condition.
Visual Inspection Chart:
2. Visually inspect for obvious signs of mechanical or electrical damage.
3. As pinpoint tests and measurements are being carried out, be sure to inspect for any disconnected, loose-fitting or incorrectly installed component, module and in-line electrical connectors and pins.
4. If the inspection reveals obvious concerns that can be readily identified, repair as necessary.
5. NOTE: Make sure to use the latest scan tool software release.
If the cause is not visually evident, connect the scan tool to the data link connector (DLC).
6. NOTE: The vehicle communication module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM.
If the scan tool does not communicate with the VCM:
- check the VCM connection to the vehicle.
- check the scan tool connection to the VCM.
- refer to Information Bus (Module Communications Network), No Power To The Scan Tool, to diagnose no communication with the scan tool.
7. If the scan tool does not communicate with the vehicle:
- verify the ignition key is in the ON position.
- verify the scan tool operation with a known good vehicle.
- refer to Information Bus (Module Communications Network) to diagnose no response from the powertrain control module (PCM) or electronic automatic temperature control (EATC) module.
8. Carry out the network test.
- If the scan tool responds with no communication from one or more modules, refer to Information Bus (Module Communications Network).
- If the network test passes, retrieve and record the continuous memory diagnostic trouble codes (DTCs).
9. Clear the continuous DTCs and carry out the self-test diagnostics from the PCM or EATC.
10. NOTE: Some PCM DTCs may inhibit air conditioning (A/C) operation. If any PCM DTCs are retrieved, diagnose those first. REFER to Computers and Control Systems.
If the EATC DTCs retrieved are related to the concern, go to the EATC Diagnostic Trouble Code (DTC) Index. If the PCM DTCs retrieved are related to the concern, go to Computers and Control Systems. For all other DTCs, refer to Body Control Systems (Multifunction Electronic Control Module). Diagnostic Trouble Code Tests and Associated Procedures
11. If no DTCs related to the concern are retrieved, GO to Symptom Chart. Symptom Related Diagnostic Procedures
Electronic Automatic Temperature Control Module - Scan Methods
The electronic automatic temperature control (EATC) system must be diagnosed by first retrieving any DTCs, if present.
- An on-demand (hard fault) DTC indicates that the fault is currently present. An on-demand DTC suggests a wiring fault, disconnected connector or component failure.
- A continuous (intermittent) DTC alone (corresponding on-demand DTC is not present) indicates that the fault is an intermittent condition and may not be currently present. A continuous only DTC suggests a poor wiring connection, loose pin or terminal or intermittent component failure.
On-demand (hard fault) or continuous (intermittent fault) DTCs can be retrieved using a scan tool. If using a scan tool, refer to the scan tool operating manual.
On-demand DTCs can also be retrieved by carrying out the Electronic Automatic Temperature Control Module On-Demand Self Test. To retrieve and/or clear continuous DTCs carry out the Electronic Automatic Temperature Control Module - Retrieve Continuous DTCs procedure. Always carry out the Electronic Automatic Temperature Control Module On-Demand Self Test before retrieving continuous DTCs.
If no DTCs are present, GO to Symptom Chart for the appropriate diagnostic action. Symptom Related Diagnostic Procedures
Electronic Automatic Temperature Control Module On-Demand Self-Test
The EATC module on-demand self test will retrieve on-demand (hard fault) DTCs only, it will not retrieve continuous DTCs. Continuous DTCs can be cleared when exiting the EATC module on-demand self test. Make sure to retrieve continuous DTCs by carrying out the Electronic Automatic Temperature Control Module Retrieve Continuous DTCs procedure before clearing any continuous DTCs.
- The EATC module on-demand self test will not detect concerns associated with data link messages like engine coolant temperature or vehicle speed signals. A scan tool must be used to retrieve these concerns.
- The EATC module on-demand self test will detect concerns in the system control functions and will display on-demand (hard fault) DTCs for concerns that are present during the self-test. The vehicle interior temperature should be between 4°-38°C (40°- 100°C) when performing the self-test. If the temperatures are not within the specified ranges, false DTCs may be displayed.
- The self-test can be initiated after cycling the ignition switch from OFF to ON. Normal operation of the climate control system stops when the self-test is activated.
- To enter the self-test, press the OFF and FLOOR buttons simultaneously and release, then press the AUTO button within 2 seconds. The display will show a flashing blower icon for 20 seconds, after which all vacuum fluorescent segments will be displayed if there are no on-demand DTCs present. If DTCs are present the EATC module will display 00 00 and then on-demand DTCs. Record all DTCs displayed.
- If any DTCs appear during the self-test, carry out the diagnostic procedure. Refer to the Electronic Automatic Temperature Control Module Diagnostic Trouble Code Index and follow the ACTION for each DTC given. Diagnostic Trouble Code Tests and Associated Procedures
- If a condition exists but no DTCs appear during the self-test, GO to Symptom Chart Condition: The EATC System Is Inoperative, Intermittent or Incorrect Operation. Symptom Related Diagnostic Procedures
- To exit the self-test and retain all continuous DTCs, press any button except DEFROST. The EATC module will exit the self-test and retain all continuous DTCs.
- To exit the self-test and clear all continuous DTCs, press the DEFROST button. The EATC module will exit the self-test and all continuous DTCs will be cleared.
- Always exit the self-test before powering the system down (system turned OFF). Once the self-test is exited the ignition switch must remain ON for at least 30 seconds to allow the temperature blend door actuators to automatically recalibrate.
- Continuous DTCs will be deleted after 80 ignition switch ON cycles after the intermittent fault occurs.
Electronic Automatic Temperature Control Module - Retrieve Continuous DTCs
The EATC module will retrieve only continuous (intermittent) DTCs when carrying out this procedure.
- Retrieval of continuous DTCs can be initiated after cycling the ignition switch from OFF to ON. Normal operation of the climate control system stops when retrieving continuous DTCs.
- To retrieve continuous DTCs, press the OFF and PANEL buttons simultaneously and release, then press the AUTO button within 2 seconds. All vacuum fluorescent segments will be displayed if there are no continuous DTCs present. Continuous DTCs are indicated by the presence of the degrees Celsius symbol (°C) on the EATC module display. Record all DTCs displayed.
- If any DTCs appear, carry out the diagnostic procedure. Refer to the Electronic Automatic Temperature Control Module Diagnostic Trouble Code Index and follow the ACTION for each DTC given. Diagnostic Trouble Code Tests and Associated Procedures
- If a condition exists but no DTCs appear, GO to Symptom Chart Condition: The EATC System Is Inoperative, Intermittent or Incorrect Operation. Symptom Related Diagnostic Procedures
- To exit and retain all continuous DTCs, press any button except DEFROST. The EATC module will exit the retrieve continuous DTCs mode and retain all continuous DTCs.
- To exit and clear all continuous DTCs, press the DEFROST button. The EATC module will exit the retrieve continuous DTCs mode and all continuous DTCs will be cleared.
- Always exit the procedure before powering the system down (system turned OFF). Once the procedure is exited the ignition switch must remain ON for at least 30 seconds to allow the temperature blend door actuators to automatically recalibrate.
- Continuous DTCs will be deleted after 80 ignition switch ON cycles after the intermittent fault occurs.
Electronic Automatic Temperature Control (EATC) Module Cold Boot Process
The purpose of the cold boot process is to allow the EATC module to re-initialize and calibrate the actuators. To carry out the cold boot process, follow the steps below.
1. Turn the ignition switch to the OFF position.
2. Disconnect the EATC module electrical connectors.
3. Wait one minute.
4. Connect the EATC module electrical connectors.
5. Turn the ignition switch to the ON position.
6. Select any position except OFF on the EATC or EMTC module.
The EATC module will now initialize and calibrate the actuators. Calibration of the actuators will take approximately 30 seconds.